Nested selectors inside plain selectors

[Machy8]

const plainSelectors = {
  'article': {
   _: 'font-size:16px', // Generates article => font-size:16px
    'h1, h2, h3, h4': 'font-size:48px' // generates article h1, article h2, ... => font-size 48px
  }
}